Charged particle beam imaging system, such as an electron beam imaging (EBI) system, is increasingly applied in advanced IC chip manufacturing. The detection resolution of EBI is high enough to detect tiny physical defects beyond the ability of optical defect imaging systems, and the EBI can be used to detect electrical defects of integrated circuitry, such as an open defect, a short or a leakage defect underneath the wafer surface by detecting voltage contrast (VC) due to the surface charge induced gray level (GL) variation.
In dynamic random access memory (DRAM) manufacturing, electrical short between neighboring storage node (SN) cylinders and/or conductive contact plugs, which arc underneath the SN cylinders, are fatal, where the latter is called a piping defect. In such scenarios, it is difficult to detect the electrical short defect because the VC difference between normal and defective cylinders is very small. Moreover, the detection of the short defects is getting more difficult under the trend of the miniaturization of DRAM and large aspect ratio of the SN cylinder.